est_pg_tune.sh

#!/bin/bash

#set -x
#set -e

page_size=`getconf PAGE_SIZE`
phys_pages=`getconf _PHYS_PAGES`
phys_memory_kb=$[ $phys_pages * $page_size / 1024 ]
kb_pct=$[ 1024 / 100]

# find the hugepage line in meminfo and keep only the number of kB
huge_page_size=`awk '/^Hugepagesize:.*kB$/{print $2}' /proc/meminfo`
peak_mem=`awk '/VmPeak:.*kB$/{print $2}' /proc/$(cat /var/run/postgresql/9.6-main.pid)/status`

## estimate peak memory
#peak_mem=$[ $phys_memory_kb / 10 * 4]

shmall=`expr $phys_pages / 2`
shmmax=`expr $shmall \* $page_size`

read -r -d '' sysctrl_conf <<- EOM
        ####################################
        # /etc/sysctl.d/40-postgresql.conf
        ####################################

        # constaint settings
        vm.swappiness = 10             # discurage swap don't turn it off?
        vm.overcommit_memory = 2       # do not overcommit (go up to 1.5 ram allocation)

        # set how much memory a process can hove
        kernel.shmmax = $shmmax         #(default: `sysctl -n kernel.shmmax`)
        kernel.shmall = $shmall         #(default: `sysctl -n kernel.shmall`)

        # set max large memory allocation the kernel can make
        # note: shows up at > 8GB RAM, inefficiant use
        # default: `sysctl -n vm.nr_hugepages`
        vm.nr_hugepages = $[ $peak_mem / $huge_page_size +1]


        # when to start cleaning dirty io blocks
        # note: try not to overwhelm your disk's cache results in platues of buffers written, write early
        # default:  $(sysctl -n vm.dirty_background_ratio) -> $(numfmt --to=iec-i --suffix=B $(sysctl -n vm.dirty_background_bytes))
        wvm.dirty_background_ratio  = 2   # vm.dirty_background_bytes =  $(numfmt --to=iec-i --suffix=B $[ $phys_memory_kb * 2 * $kb_pct ])

        # when to stop prcesses to cleaning dirty io blocks
        # default: $(sysctl -n vm.dirty_ratio) -> $(numfmt --to=iec-i --suffix=B $[ $phys_memory_kb * $(vm.dirty_bytes) * $kb_pct])
        vm.dirty_ratio = 10             # vm.dirty_bytes = $(sysctl -n vm.dirty_bytes)


EOM
echo "$sysctrl_conf"

echo -e "\n\n\n"

read -r -d '' grub_conf <<- EOM
        #################################
        # /etc/grub.d/99-postgresql-HTP.conf
        #################################
        transparent_hugepage=never
        echo never > /sys/kernel/mm/transparent_hugepage/enabled
EOM
echo "$grub_conf"

echo -e "\n\n\n"w

[https://www.slideshare.net/PostgreSQL-Consulting/linux-tuning-to-improve-postgresql-performance]
[https://www.slideshare.net/fuzzycz/postgresql-on-ext4-xfs-btrfs-and-zfs]
[https://blog.pgaddict.com/posts/postgresql-io-schedulers-cfq-noop-deadline]
[https://blog.pgaddict.com/posts/postgresql-performance-on-ext4-and-xfs]

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